The present invention relates to antifungal compositions, particularly to biological control compositions containing Trichoderma harzianum and to methods of protecting plants from pathogenic fungi Botrytis cinerea and Sclerotinia sclerotiorum with such compositions.
Gray mold, incited by Botrytis cinerea Pers. Fr.; and white rot incited by Sclerotinia sclerotiorum Lib: de Bary are serious problems in many crops around the world. The pathogen attacks many crops including grapes, vegetables and ornamentals. Crops are attacked when grown in the open or in structures under cover. If not adequately controlled, gray mold and white rot can cause substantial pre-harvest as well as post-harvest losses at storage and transport. The pathogens attack all parts of the plants including flowers, fruits, leaves, stems, branches, phyloclades, bulbs or seeds.
Chemical fungicides are widely used to control the disease. However, B. cinerea has developed resistance to common fungicides used. Among these are dicarboxyimide fungicides and benzimidazole fungicides. In many places, farmers do not have any solution for the problem because of resistance and in other places or crops this is likely to happen in the future.
Gray mold and white rot epidemics are usually severe when high humidity, temperatures between 10.degree. C.-25.degree. C. and wetness over the sensitive organs of the plant prevail.
The use of antagonisitic micro-organisms in controlling plant pathogenic fungi has been the subject of extensive research. One of the most frequently studied antagonists in relation to biological control is the genus Trichoderma (Y. Elad et al., 1982, Can. J. Microbiol. 28: 719-725; I. Chet and R. Baker, 1981, Phytopathology 71:286-290; M. N. Schroth and J. G. Hancock, 1981, Ann. Rev. Microbiology 35: 459-463; Y. Elad et al., 1981, Plant Disease 65: 675-677; Y. Elad et al., 1980, Phytopathology 70: 119-121; I. Chet et al., 1979, in B. Scrippers and W. Gams. eds., Soil Borne Plant Pathogens", Academic Press, N.Y., N.Y.; Y. Hadar et al., 1979, Phytopathology 69: 64-68; C. Dennis and J. Webster, 1971, Trans. Br. mycol. Soc. 57 (3), 363-369: Y. Elad., (1990) Phytoparasitica, 18:99-105).
Species of strains of Trichoderma may be differentially antagonistic to different species of fungi (H. D. Wells et al., 1972, Phytopathology 62: 442-447). Such differences in antagonism have been found both within and between species of Trichoderma (D. K. Bell et al., 1982, Phytopathology 72: 379-382). Therefore each isolate of Trichoderma, regardless of its species, has different features in abilities to contract plant diseases.
B. cinerea and S. sclerotiorum are sensitive to antagonism by competition of other microorganisms. Germination of spores and growth of hyphae of this plant pathogen and infection of host plants can be reduced when nutrients and space are limited. Such a mechanism can be a basis for successful biological control of gray mold and white rot. More-over, the antagonist should be able to survive in the same niche for a long time and be active against the pathogen at the same time.